It's difficult to memorize the new word's correct pronunciation.
And the teacher hasn't any time to revise the vocab for us in the classroom.
So, what can we do if I learn the new word without the help of others especially the English teacher?
So, I think the phonetics is the basic tool for ESL learner to learn and improve their English.

Yes, you are right. Phonetics is the best tool for learning English if you don't want help from others. There is another, so many tools available in the market for learning English. http://matadornetwork.com/abroad/30-free-online-resources-for-teaching-and-learning-esl/